The present invention relates to locks which are operable by a key between locked and unlocked conditions and in particular to locks wherein once the key is used to place the lock in an unlocked condition the lock prevents removal of the key from the lock until the lock is returned to a locked condition.
Utility services such as electric service, telephone service and cable television service are commonly provided to residential and commercial users. In providing these services enclosures such as utility boxes are used to enclose the electrical and other equipment needed to provide the service. For example, in an apartment complex each apartment's cable television hook-up will be located in a common utility box.
Utility boxes are normally locked so that only authorized servicemen will have access to the contents. A problem has arisen however in that the servicemen, which are often times subcontractors of the utility provider, will leave the utility boxes unlocked after completing their work and may not even close the utility box door. When the utility box is left open, cable lines and other electrical equipment are left exposed whereby they may be easily damaged and may injure children and others. Even where the utility box is closed, but left unlocked, anyone may have access to the utility box which not only creates the hazard of potential injury, but most commonly encourages and enables the theft of the utility service by an unauthorized user. In the example of an apartment complex, all apartments are normally wired for cable television service. All that is needed to provide the cable service to a particular apartment is to make the proper hook-up in the utility box. When the box is left unlocked, the apartment dweller may easily make this hook-up himself without the knowledge of the cable company, thereby obtaining free and unauthorized cable television service. Similar problems are also encountered with cabinets, vending machines and any other enclosures which are intended to have limited access to only authorized personnel.
It has therefore been found desireable to provide a lock which requires a key to unlock the enclosure, whereby once the lock is unlocked the lock will trap the key within the lock preventing the removal of the key until the enclosure is securely closed and the lock is returned to a locked condition. A serviceman will therefore be required to close and lock the enclosure before he can remove his key. The enclosure keys may be issued and returned daily to the owner of the enclosures so that the owner may monitor whether any keys are being left in enclosures and by whom.